Part Number: LM393
Other Parts Discussed in Thread: LM339
A pcb was designed for us where an lm393 comparator uses negative feedback res 5.1k neg in to output of the 393--The 393 positive in of the comparator is connected directly to 12 V pull up res.(10K) --The 393 pos input is connected to a hall type encoder and its output is connected to the in port of a MCU----I have been in electronics for over 60 years I have never seen a comparator use neg feed back---The comparator oscillates with an input voltage between the ref voltage =3V and the modified ref voltage due to the neg feed back of 1.7V---The voltage divider to set up for a 3V ref (the divider is a 15K and a 5.1K connected to 12V providing a 3V ref)---When the comparator goes low it puts the feedback resistor in parallel with the existing 5.1K divider providing a new ref V of 1.77V so the comparator oscillates between the 3V ref and the1.77ref when the input voltage is between those levels. My question is there ever an application to design a comparator with negative feedback. I will send you a cut and paste of the schematic if needed----Thanks Mike T
